Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Fls perfect, epigynous; hypanthium well developed, lined with a nectary that is shallowly lobed at the summit alternate with the stamens; tep mostly 5, appearing as lobes on the hypanthium, each bearing a tuft of hairs behind and ± adherent to the stamen; ovary unilocular; placental column geniculate near midlength; stigma capitate; ovules mostly 3; fr a dry drupe, subglobose or with a short neck at the top, surmounted by the persistent sep; glabrous low perennial herbs, colonial by rhizomes, with rather small, alternate or scattered, subsessile or short-petiolate lvs and terminal cymose-paniculiform infls of small fls. 2, the other in Eur.